The invention relates to a method of and to an apparatus for making a stream of fibrous material, especially tobacco. More particularly, the invention relates to improvements in methods of and in apparatus for making a stream which contains tobacco shreds as well as tobacco ribs and which can be converted into the filler of a tobacco-containing rod, e.g., a cigarette rod which is ready to be subdivided into plain cigarettes of unit length or multiple unit length.
It is known to gather tobacco shreds into an elongated flow of loose tobacco particles and to convey the flow along an elongated first path. Successive increments of the flow are transferred into a second path wherein the transferred increments constitute successive increments of a relatively dense elongated stream which is ready to be trimmed or equalized and draped into a web of cigarette paper or other suitable wrapping material. The transfer of successive increments of the flow of loose tobacco particles into the second path takes place in a so-called stream building zone wherein the second path normally extends transversely of the first path. The thus obtained stream is advanced axially or lengthwise toward and through a trimming station and thereupon through a wrapping station before it reaches a so-called cutoff which subdivides the wrapped tobacco filler (i.e., the trimmed or equalized and wrapped stream) into a series of discrete rod-shaped articles, e.g., into plain cigarettes of unit length or multiple unit length.
Tobacco shreds are loosened in a so-called distributor (also called hopper) which defines the first path and is equipped with means, such as nozzles which discharge jets of compressed air and/or one or more suction conveyors, for advancing the flow along the first path toward and into the stream building zone. The second path is normally defined by an endless foraminous belt conveyor which is adjacent a suction chamber and has an elongated stretch confined in a tobacco channel and defining with the latter the aforementioned stream building zone. The channel is located upstream of a trimming or equalizing device which removes the surplus so that the stream is converted into a rod-like filler which is ready to be draped into a web of cigarette paper or other suitable wrapping material.
The flow of loose tobacco particles contains tobacco shreds as well as at least some tobacco ribs. The ribs are relatively stiff and are likely to affect the quality of the wrapped filler, especially if they are permitted or caused to accumulate in the outer portion of the filler. Such ribs can puncture the very thin wrapping material to thus permit uncontrolled penetration of atmospheric air into a rod-shaped product containing the respective portion of the wrapping material. Moreover, non-uniform or unpredictable distribution of tobacco ribs in the filler of a tobacco rod affects the quality of the product. For example, relatively large tobacco ribs are likely to be combusted at a rate which is slower than the rate of combustion of smaller ribs and/or shreds so that glowing large ribs can project beyond the lighted end of a partially consumed cigarette and can fall onto the ground with the resulting danger of fire or damage to the floor or floor covering. Therefore, it is desirable to ensure a highly predictable distribution of tobacco ribs among the shreds as well as to prevent penetration of relatively large ribs into that portion of the path for acceptable comminuted tobacco particles (shreds) in which the filler is formed and draped into cigarette paper or the like.